Question

已知x的2次方减2x=1,求（x-1）（3x+1）-(x+1）的2次方的值

Answer 1

x^2-2x=1

x^2-2x-1=0

(x-1)(3x+1)-(x+1)^2

=3x^2-2x-1-x^2-1-2x

=2x^2-4x-2

=2(x^2-2x-1)

=2*0

=0